I'm just curious if anyone knows the connecting rod length.

Dave wrote on 01/03/16 at 16:10:29:

factory service manual

Someone needs to post on a huge posterboard...

[b Hmmm.... like that $20 t-shirt advertisement I'm looking at.... yeah, you know, those shirts that no one's getting anyway ... Just take that silly thing down and replace it with something like this:
[/b]
"Please!, Someone!, Anyone! Tear down an LS650 engine, carefully measure the connecting rod dimensions, and post it here at their earliest convenience! The Savage community needs your measurements!"

Perfect!

Oh! Mysterious John is going to hate me!

Im curious to know what caused the curiosity.

The idea is that a longer rod will be easier on the engine than a short con rod as far as piston acceleration forces are concerned.

We're trying to figure out how the Savage has such a red line of 6500 and a stroke of 3.7 inches. That's some tough piston forces, and this engine does 4000 rpm all day long on the highway. Compared to car engines, this is very stressful.

We are trying to see how rod/stroke ratio plays into all this.

I don't see rod length as important. Crank throw determines piston speed.
A one inch rod on a crank with a 1/2 " throw is gonna have the same piston speed if you put a foot long rod on it. YOu could share the information about the rpod length affecting piston/engine .

LOOK! LOOK! LOOK! Here it is!  

http://www.motoiq.com/MagazineArticles/ID/1996/Does-Length-Matter.aspx

Take an old junked-out briggs 5 hp flathead and spin the crank. Watch how the piston acts as it reaches TDC and BDC. I bet you might be able to watch the effect firsthand. I'm not exactly sure I've done this before with that in mind, but remembering seeing the piston move from years ago, I bet you might be able to see it.

Imagine this: The crank is turning and the con rod is slanting. As it's slanting, it's yanking the piston downward faster than you would expect the crank journal alone to do. Also, when it's traveling upward, the rod snaps the piston upwards to TDC. It does this by leverage. It has to do with the angle of the con rod. If the con rod were straight all the time, only the crank journal would have an effect, but then you would have to create a slot, like a scotch yoke. But the angle of the con rod affects the leverage of the system. This leverage changes as the crank moves and the con rod angle changes.

Now the angle is going to be steeper with a short con rod than with a long one. Imagine extremes here. If the con rod were ridiculously short, then it would be angled crazy steep at 90 degrees. An incredibly long one wouldn't have much angle at all. Say a 10 foot long rod with a 2 inch stroke wouldn't move all that much compared to a 2 inch rod (which might be too short to work anyway).

Imagine our thumper with the piston halfway down  the rod journal sideways. That con rod is going to be at an angle to reach from the wrist pin to the crank journal, now isn't it?   Now which is going to be angled steeper, the long or short rod? Distance traveled is the same as far as the rod journal is concerned. Now we're just talking about the distance from the wrist pin to the journal and the angle of that.

Think of a circle cut into slices. If you have a big circle, the size of an arc (the outside bit of circumference) is going to be pretty big for a thin (small angle) slice. A small circle is going to need a really fat slice (wide angle).

The steeper the angle, the harder the con rod yanks on the piston near TDC, making it stay near TDC for less time. The rod journal is kinda pulling things sideways, collapsing the conrod/crank journal/wrist pin complex, and yanking or snapping the piston downward.

This leverage thing actually works backwards near BDC, making the piston stay close to BDC longer than otherwise.

Again, if there are any mechanical engineers out there, you're welcome to help out here.

I hope that helps